Hi everyone, I have a model which yields a qqnorm plot (residuals~fitted values) of a sigmoidal shape. I have been reading about link functions and leafing through Crawley, but I'm still not sure how to solve this. Perhaps "family=quasi(power=...." is the best route? Any suggestions much appreciated. Simon Pickett PhD student Centre For Ecology and Conservation Tremough Campus University of Exeter in Cornwall TR109EZ Tel 01326371852